Understanding effective post‐test linkage strategies for HIV prevention and care: a scoping review

Abstract Introduction Following HIV testing services (HTS), the World Health Organization recommends prompt linkage to prevention and treatment. Scale‐up of effective linkage strategies is essential to achieving the global 95‐95‐95 goals for maintaining low HIV incidence by 2030 and reducing HIV‐related morbidity and mortality. Whereas linkage to care including same‐day antiretroviral therapy (ART) initiation for all people with HIV is now routinely implemented in testing programmes, linkage to HIV prevention interventions including behavioural or biomedical strategies, for HIV‐negative individuals remains sub‐optimal. This review aims to evaluate effective post‐HTS linkage strategies for HIV overall, and highlight gaps specifically in linkage to prevention. Methods Using the five‐step Arksey and O'Malley framework, we conducted a scoping review searching existing published and grey literature. We searched PubMed, Cochrane Library, CINAHL, Web of Science and EMBASE databases for English‐language studies published between 1 January 2010 and 30 November 2023. Linkage interventions included as streamlined interventions—involving same‐day HIV testing, ART initiation and point‐of‐care CD4 cell count/viral load, case management—involving linkage coordinators developing personalized HIV care and risk reduction plans, incentives—financial and non‐financial, partner services—including contact tracing, virtual—like social media, quality improvement—like use of score cards, and peer‐based interventions. Outcomes of interest were linkage to any form of HIV prevention and/or care including ART initiation. Results Of 2358 articles screened, 66 research studies met the inclusion criteria. Only nine linkage to prevention studies were identified (n = 9/66, 14%)—involving pre‐exposure prophylaxis, voluntary medical male circumcision, sexually transmitted infection and cervical cancer screening. Linkage to care studies (n = 57/66, 86%) focused on streamlined interventions in the general population and on case management among key populations. Discussion Despite a wide range of HIV prevention interventions available, there was a dearth of literature on HIV prevention programmes and on the use of messaging on treatment as prevention strategy. Linkage to care studies were comparatively numerous except those evaluating virtual interventions, incentives and quality improvement. Conclusions The findings give insights into linkage strategies but more understanding of how to provide these effectively for maximum prevention impact is needed.

Effective linkage is important as PLHIV on ART who are engaged in care and virally suppressed prevent onward HIV transmission and have improved quality of life [7][8][9].Modelling suggests that prompt linkage to ART could reduce HIV incidence by 54% and mortality rate by 64% in the United States [10], and is further estimated that with 92% linkage to ART, HIV incidence would decline from 2.5% to 0.03% within 30 years in South Africa [11].Therefore, WHO provides HIV guidance that outlines appropriate services to be offered according to local epidemiology, individual HIV risk and client needs [12].
In addition, HIV-negative individuals with a high ongoing risk for HIV may benefit from a range of prevention interventions, such as voluntary medical circumcision (VMMC), partner services and pre-exposure prophylaxis (PrEP) [13][14][15][16].Due to the diversity of prevention interventions, linkage strategies also need to be tailored as not all people testing negative require onward services [17].Evidence to support effective HIV prevention linkage strategies remains limited and often not prioritized.Challenges such as lack of evidence and competing priorities impede the achievement of the UNAIDS target for 95% of people with HIV risk to receive combination prevention [2].Consequently, implementation of linkage to prevention services is suboptimal, leaving many with high HIV risk unreached.Furthermore, integration of linkage strategies following HTS may be useful for other conditions, such as sexually transmitted infections (STIs), viral hepatitis and non-communicable diseases (e.g.hypertension and cancers).
We, therefore, conducted a scoping review to assess strategies and best practices for linkage to HIV prevention (main objective) and care (secondary objective).This review provides a summary of the evidence, as well as critical implementation and research gaps.

M E T H O D S 2.1 Study design
We conducted this scoping review following the Preferred Reporting Items for Systematic Reviews and Meta Analyses-Extension for Scoping Reviews (PRISMA-ScR) checklist (Appendix S1) [18].We utilized the Arksey and O'Malley framework [19], where these five steps were followed: (1) identifying a clear research objective and search strategies; (2) identifying relevant research articles; (3) selection of research articles; (4) extraction and charting of data; and (5) summarizing, discussing, analysing and reporting the results.

Literature search strategy
We searched the following online databases for literature published between 1 January 2010 and 30 November 2023: PubMed, Cochrane Library, CINAHL, Web of Science and EMBASE.We developed a search string using the appropriate MeSH terms supported by free-text formats in the PubMed search builder.The final search string consisted of the core concepts (HIV Testing) AND (Linkage/Prevention/Care). The search string was then adapted to the other electronic databases (Appendix S1).
We also conducted a search of the grey literature directed at 19 major international funders and advocacy organizations involved with HIV programming identified as potential repositories (e.g.The Global Fund, Bill & Melinda Gates Foundation and Treatment Action Campaign).We searched trial registries for ongoing or completed studies and contacted investigators to obtain results that were close to publication.Linkage data were also solicited from national programmes, key experts and donors including any relevant peer-reviewed literature that was missed in the systematic search.We iteratively revised the extraction and analysis plan as we reviewed the literature.

Eligibility criteria
We included original, peer-reviewed research studies, published clinical or programme reports, and grey literature in English.These studies evaluated linkage to prevention and care using seven delivery approaches, namely case management, streamlined, partner services, incentives, virtual, peerbased and QI interventions, reflecting discussions at the WHO on the most appropriate delivery approaches (Table 1).We excluded studies not written in English and those that did not meet the inclusion criteria based on study dates and intervention strategy.

Outcomes
The main outcomes of interest were: (1) linkage to prevention-defined as connecting HIV-negative individuals to relevant post-test services [3]; (2) linkage to care-defined as accessing care at an HIV clinic after a positive HIV diagnosis measured either by the first clinic attendance date, first CD4 cell count, viral load date [23]; or ART initiation-defined as starting ART after an HIV-positive result [3].Costs associated with linkage to prevention and care were also of interest.

Data extraction
Two authors (PC and BW) were involved in literature selection and data extraction.Covidence TM was used to upload data from the search databases before the removal of duplicate citations and article extraction onto an Excel spreadsheet.
The extraction sheet contained citation elements (title, year of publication), location (country, WHO region), study design, results and size estimates where applicable.Costing information was also included where applicable.We adjusted costs to 2021 United States Dollars (USD$) using the Gross Domestic Product deflator [24].Disagreements on the inclusion or exclusion of literature were resolved by consensus, and, if that failed, a third independent reviewer (CJ) resolved the disagreement.

Analysis
Data from the extraction sheet were first categorized into linkage to prevention and care then by delivery approach and study design, before being used to develop the manuscript.
Introduced in 2018 WHO guidance and updated in 2019.Included to identify new evidence and use in prevention context.

Incentives
Financial or non-financial rewards for linking to HIV care or prevention [21] Previously reviewed in 2019 WHO guidance and addressed use in a good practice statement.Included to update evidence review of care and prevention.

Virtual interventions
Interventions that include social media, videos, text messaging, phone calls and computerized platforms [3] Previously reviewed in 2019 and 2021 WHO guidance and addressed use in a good practice statement.Included to update evidence review of care and prevention.

Peer-based
Interventions that enlist specific populations to support others to engage in services and adopt healthy lifestyles [22] Previously reviewed in 2018 and 2019 WHO guidance.Included to update evidence review of care and prevention.Partner services Involves partner notification, contact tracing, index testing and family-based index case testing for reaching the partners of people living with HIV and includes network-based testing approaches [13] Previously reviewed in 2019 WHO guidance.
Included to update evidence review of care and prevention.
Quality improvement Solutions to prevent errors and defects during HIV service delivery, for example score cards, plan-do-study act cycles [3] Previously reviewed in 2018 WHO guidance.Included to update evidence review of care and prevention.

Multiple interventions
Combinations of more than one delivery approach mentioned above Included to account for studies evaluating more than one intervention.
a Support for disclosure was evaluated under partner services.Demand creation was excluded from this review due to the shift in focus at the WHO towards targeted HIV Test and Start programmes.
Qualitative data summarizing findings on the delivery approaches were grouped thematically.

Search results
Figure 1 indicates the search results and study selection process [25].The search strategy yielded 2358 citations (including 12 grey literature) of which 199 full-text articles were assessed for eligibility.Of these, 66 articles met our inclusion criteria: nine (14%) on linkage to prevention and 57 (86%) on linkage to care (Tables 2-7).

Geographic distribution of the studies
Figure 2 represents the geographic distribution of the studies with none reported from the Eastern Mediterranean region.Among the nine linkage to prevention studies, five were from Africa and four were from the United States.Among the linkage to care studies, 60% were conducted in Africa (n = 34/57) and 28% in the Americas (n = 16/57).

Delivery approaches
Among linkage to prevention studies, case management, partner services and peer-based models were the most commonly used delivery approaches (each at 22%, n = 2/9) (Figure 4).For linkage to care studies, case management (21%, n = 12/57) was most commonly described especially in the Americas, followed by streamlined and multiple interventions (each at 19%, n = 11/57), especially in Africa.

Linkage to prevention
Nine linkage to prevention studies were conducted in Africa and the United States (Tables 2 and 4).Gaps in WHO recommendations on linkage to prevention are summarized in Table 7.Studies conducted in Africa were all among heterosexual individuals and focused on linkage to PrEP, VMMC, STI and cervical cancer screening [26,28,29,31,33,35].USbased studies evaluated PrEP linkage among key populations [27,30,32,34].No linkage to HIV prevention study reported on QI.

RCTs
Peer-based: Two RCTs evaluated peer-based interventions (22%, n = 2/9).In a peer-based RCT among heterosexual adults in Zambia, there was increased VMMC uptake and cervical cancer screening among participants who received an enhanced referral and additional escort relative to those receiving routine counselling [26].In a peer-based RCT conducted in the United States, men who have sex with men (MSM) who received a training workshop and a series of check-in phone calls had improved PrEP initiation compared to those who only attended a sexual risk assessment workshop [27].

Multiple interventions:
Two RCTs evaluated multiple interventions (22%, n = 2/9).In a Malawi-based cluster RCT, male partners of female antenatal care (ANC) attendees who received invitation letters, HIV self-testing (HIVST) and financial incentives had higher VMMC referrals compared to those who received invitation letters only [28].In an RCT conducted in South Africa and Uganda, men receiving either text message reminders or lay counsellor follow-up were more likely to be circumcised compared to those receiving standard clinic referrals [29].
Virtual interventions: One study (11%, n = 1/9), a USbased RCT, showed improved PrEP initiation among MSM who received phone-based counselling from providers within 24 hours of opening electronically tagged HIVST kits compared to those receiving HIVST without electronic beacons [30].
Case management: One study (11%, n = 1/9), a US-based RCT, showed no improvement in PrEP initiation among MSM receiving strengths-based case management compared to those receiving an information package on HIV prevention strategies [31].
Partner services: One study (11%, n = 1/9), a South Africabased RCT, had fewer male sex partners initiating PrEP after receiving HIVST kits from their female partners compared to those invited to the facility for HTS [32].                  1. Letter and clinic access together with two prequalified oral HIVST kits for the woman to take home for her male partner ("ST").
5. Included a phone call to the male partner on the day the woman enrolled ("ST + reminder").
Standard of care: Clinic invitation letter to the male partner Costing: All resources were costed and used to estimate the total costs.Total costs were divided by the total number of men who tested for HIV and attended a male-friendly clinic (MFC) to estimate the cost per male partner who tested for HIV and attended an MFC, and by the total number of men who started ART or were referred for VMMC to estimate the cost per male partner who tested for HIV and either started ART or was referred for VMMC.

USD
The average cost per male partner who started ART or was referred for VMMC for the five intervention arms ranged from $106 (ST  annual discounting.Estimated the proportion of cases of HIV detected during early primary infection, reduction in HIV incidence and prevalence, incremental cost-effectiveness ratio (ICER) and net monetary benefit.

USD
Sabes had an ICER of $1580 per QALY compared to SOC.Intervention costs were $7613 per early primary infection diagnosed.
Abbreviation: HIVST, HIV self-testing; MSM, men who have sex with men; PMTCT, prevention of mother to child transmission; RCT, Randomized controlled trial

Linkage to HIV prevention
Case management [33] Additional support for accompanied referrals and fast-tracking encouraged clients to access PrEP Some providers did not complete screening if they perceived clients to be at low risk for HIV, or if they had a heavy workload Linkage to HIV care Incentives [85][86][87] Cash incentives were appreciated.
Other options to access healthcare were available, for example walking, or borrowing money to go to facilities Cash incentives introduce moralizing discussions on who can be influenced and what can be bought Case management [88] Patients saw the case manager/linkage coordinator as an accessible healthcare specialist helping them navigate complicated healthcare systems.
Lack of psychological support from health providers was a key challenge Virtual [73,89] Mobile phone app to facilitate HIVST showed great potential Virtual platforms using texts (WhatsApp and SMS) to support peer mentorship were appreciated by adolescents and young adults Participants preferred models allowing some degree of direct human interaction, for example face-to-face or through phone calls Concerns about data privacy, for example possibility of phone hacking Peer-based [90] Peer-led community-based HIV self-testing improved access to HIV testing Concerns about privacy and confidentiality of HIV test results.

Non-RCT study designs
Three studies involved non-RCT study designs (Tables 2  and 4).In a Zimbabwe-based mixed methods in evaluating case management, 98% of participants with a negative HIV result who received risk assessment and targeted followup completed their referrals and initiated PrEP [33].A US-based quasi-experimental study showed increased PrEP referral in the post-intervention period among MSM receiving streamlined service delivery after post-screening risk assessment [34].In a Kenya-based cohort study that involved contacting male partners of female ANC attendees, there was no improvement in VMMC linkage, though STI consultations were higher compared to the standard of care [35].

Cost and cost-effectiveness
Three studies, all in Africa, evaluated the costs of linking to prevention (Table 5).In Malawi, the average cost per male partner initiating ART or referred for VMMC among male sex partners to female ANC attendees ranged from US$106 (HIVST + $3 cash incentive) to US$189 (HIVST + lottery with 10% chance of winning $3 cash incentive) [28].In Zambia, the incremental cost-effectiveness ratio (ICER) comparing enhanced counselling with follow-up (arm two) and components of arm two with escort (arm three) to standard of care was $433 and $186 per disability adjusted life year (DALY) averted for linking to VMMC, respectively, and $697 and $ 122 per DALY averted for cervical cancer screening, respectively [26].In Kenya, the ICER for couples receiving home visits for HTS compared to those receiving written invitations was $1017 and $706 per DALY averted for the programme and task-shifting scenarios, respectively [81].

Qualitative values and preferences
In a Zimbabwe-based mixed methods study evaluating values and preferences among providers offering risk assessment and targeted follow-up to participants with negative HIV results, some providers purposefully did not complete Figure 3. Type of intervention by study design and WHO region.AFRO, WHO Regional Office to Africa; AMRO, WHO Regional Office to the Americas; EMRO, WHO Regional Office to the Eastern Mediterranean; EURO, WHO Regional Office to Europe; RCT, randomized controlled trial; SEARO, WHO Regional Office to South-east Asia; WPRO, WHO Regional Office to the Western Pacific.
Figure 4. Type of intervention by delivery approach and WHO region.AFRO, WHO Regional Office to Africa; AMRO, WHO Regional Office to the Americas; EMRO, WHO Regional Office to the Eastern Mediterranean; EURO, WHO Regional Office to Europe; SEARO, WHO Regional Office to South-east Asia; WPRO, WHO Regional Office to the Western Pacific.screening if they perceived their clients to be at low-risk for HIV, or if they had a heavy workload [33] (Table 6).

Linkage to care
Of the 57 linkage to care studies reported, 60% were RCTs (n = 34/57) (Tables 3 and 4).Gaps in WHO recommendations on linkage to care are summarized in Table 7. Thirty-four studies were conducted in Africa, 16 in the Americas (mainly the United States), three in Europe and two each from the Western Pacific and Southeast Asia regions (Figure 3).

RCTs
Streamlined interventions: Nine RCTs evaluated streamlined interventions (16%, n = 9/57).Three involved either widescale community-based testing [7,36,37] or facility-based HTS [38] with point-of-care (POC) CD4 cell count testing and encouraged same-day ART initiation all showed improved linkage to care and ART initiation.Three studies among pregnant women and mothers attending integrated ANC that offered ART also showed increased linkage to ART initiation [39][40][41].
Two studies that showed no effect in linkage to care included: (1) a study comparing home-based to mobile-clinic-based HTS [42]; and (2) a study evaluating HTS provided before, during or after clinical consultation [43].
Case management: Seven RCTs evaluated case management (12%, n = 7/57).Four RCTs utilizing case managers in the United States, Russia, Ukraine and Rwanda showed increased linkage to care when compared to passive referral [44][45][46][47].However, two US-based RCTs, one involving strengths-based case management among female sex workers (FSWs) and persons who inject drugs (PWIDs) [48], and the other involving intensive case management and weekly counselling sessions for 3 months [49] showed no change in linkage to care or ART initiation.In Uganda, hospitalized clients receiving inpatient HTS and case management with a personalized risk assessment and risk reduction plan were less likely to link to care compared to those receiving outpatient HTS 1 week postdischarge [50].
Multiple interventions: Five RCTs combined incentives, streamlined, virtual and/or peer-based interventions (9%, n = 5/57).Two RCTs in Mozambique and Eswatini that improved linkage to HIV care (RR > 1.5) utilized a combination intervention strategy, that is POC CD4 testing, accelerated ART initiation, mobile phone appointment reminders, health educational packages and non-cash financial incentives [51,52].In Uganda and South Africa, participants receiving conditional lottery incentives with motivational text messages had a shorter median time to ART initiation compared to those who received text messages alone [53].In two South Africabased RCTs, one evaluating combined POC CD4 testing and strengths-based case management [54], and the other evaluating same-day POC CD4 testing and text message reminders [29] showed improved linkage to ART initiation.
Incentives: Three RCTs evaluated the use of cash vouchers valued at approximately $25 (range: $4−$100) to improve linkage to care (5%, n = 3/57).One India-based RCT among PWIDs showed higher linkage to care and ART initiation among those receiving relative to the standard of care [55].
The other two RCTs that showed no effect on linkage to care included a US-based RCT among PLHIV who received cash vouchers for HIV-related tests [56], and a South Africa-based RCT where PLHIV received approximately $25 if ART was started within 3 months of HTS [57].
Virtual interventions: Three RCTs utilized either phone, text, social media or mobile phone applications (5%, n = 3/57).In Uganda, HIV-positive clients receiving motivational interviewing and counselling community health workers (CHWs) guided by a mobile phone algorithm had higher linkage to care in HIV services compared to those counselled by CHWs not guided by the algorithm [59].In Kenya, participants receiving patientcentred counselling phone calls on ART initiation from clinical officers had a higher likelihood of linking to care compared to those receiving routine counselling [58].However, in a US-based RCT among prisoners anticipating release, there was no significant difference between those who utilized computerized counselling with post-incarceration text messaging compared to those who received an instructional video predischarge [60].
Partner services: Partner services were reported in two studies in Kenya and South Africa (4%, n = 2/57).Positive results were reported in a cluster-RCT on assisted partner services in Kenya where sex partners who were immediately contacted for HTS by a healthcare worker had higher linkage to care compared to those who were contacted 6 weeks later [64].However, there was no effect on linkage to care in South Africa where fewer male sex partners initiated ART after receiving HIVST kits from their female partners compared to those receiving facility invitations [32].
Quality improvement: Two cluster-RCTs in the United States and South Africa showed no change in linkage to HIV care (4%, n = 2/57).In the United States, there was no difference in linkage to care when comparing facilities receiving HIV training and QI strategies for targeted improvements, to those that only offered HIV training [63].In South Africa, there was no difference in linkage to care when comparing facilities incorporating on-site staff mentorship and data QI activities to facilities that only offered monthly supervision and data feedback meetings [62].
Peer-based: One Zambia-based cluster RCT (2%, n = 1/57) among adult FSWs showed no effect on linkage to care when HIVST kits were delivered either directly by a peer educator or through a coupon when compared to standard HTS [61].

Non-RCTs
Linkage to care studies involving non-RCT study designs are summarized in Table 3.
Case management: Four non-RCT studies (7%, n = 4/57) evaluated case management interventions.In a Canada-based cross-sectional study offering outreach nursing teams to support ART initiation and retention, participants were six times more likely to initiate ART compared to those enrolled preintervention [65].A US-based cross-sectional study improved linkage to HIV care among PWID utilizing linkage coordinators compared to those who did not [66].A US-based cohort study among youth living with HIV receiving HIV case management at non-traditional HIV testing venues (e.g.night clubs) showed improved linkage to HIV care compared to those seen at routine adolescent clinics [67].In another US-based cohort study, transgender women who received strengths-based case management together with housing, employment and outreach-based health services were almost twice as likely to initiate and be retained in care compared to those who enrolled in the pre-intervention period [68].
Multiple interventions: Four non-RCT studies (7%, n = 4/57) evaluated multiple interventions.In a Nigeria-based nonrandomized controlled trial, 86% (n = 31/36) of young men, including MSM, who received social media enabled peernavigation support linked to HIV care [71].There was no effect on linkage to HIV care in a US-based cross-sectional study among prisoners evaluating a combined intervention of video conferencing, case management, pre-release and reentry services compared to those who did not receive the combined intervention [72].In a South Africa-based mixedmethods study, adolescents and youth receiving virtual peer support and mentorship through WhatsApp and SMS were more likely to link to care compared to matched controls [73].In a Tanzania-based programme evaluation, 97% of participants receiving peer-delivered linkage case management, treatment navigation and face-to-face counselling enrolled in HIV care [74].
Streamlined interventions: Two non-RCT studies (4%, n = 2/57) evaluated streamlined interventions.One was a Zambiabased quasi-experimental study where patients receiving integrated ART and Tuberculosis (TB) care were more likely to link to care compared to controls [69].The other was a USbased simulation study that showed improved direct referral to linkage to care among adolescents and young adults using expanded testing sites [70].
Peer-based: Two studies (4%, n = 2/57) evaluated peerbased interventions, and both showed positive results.In a Kenya-based quasi-experimental study, peer support increased linkage to care among adolescents and youth receiving fasttracked peer-navigated services and counselling at healthcare facilities and schools compared to those in the preintervention period [75].In a China-based cross-sectional study, peers to previously untested MSM were more likely to test and link to care after rapid HTS at mobile and community-based organizations compared to those who did not receive the intervention [76].
Virtual: Two studies (4%, n = 2/57) evaluated virtual interventions.In a Uganda-based cohort study, participants receiving weekly phone calls and SMS reminders were more likely to link to HIV care compared to those who did not receive the intervention [77].In Thailand, a study comparing MSM and transgender women using either online, supervised or offline HIV counselling and testing, there was lower ART initiation among participants in the online only group (52.8%) compared to those who received either facility-based HTS (offline, 84.8%) or online pre-test counselling with offline HIV testing using HIVST (mixed group, 77.8%) [78].
Quality improvement: Two studies (4%, n = 2/57) evaluated QI interventions.In a US-based quasi-experimental study, there was improved linkage to care after the implementation of a QI intervention in which pharmacists ensured ART and/or medications for opportunistic infections were ordered and administered in inpatient settings and that patients had access to medications at the time of hospital discharge com-pared to the pre-implementation phase [79].In a Ugandabased quasi-experimental study, there was improved linkage to HIV care in facilities where staff and expert patients were trained on QI compared to the pre-intervention period [80].
Partner services: One study (2%, n = 1/57) evaluated interventions which contacted partners.In a Kenya-based cohort study, there was no difference in linkage to care when comparing men contacted by their female partners who had attended ANC to those who received a clinic invitation letter [35].

Cost and cost-effectiveness
Five linkage to care studies reported on cost (9%, n = 5/57) (Table 5).In Uganda where staff and expert patients were trained on QI, the annual cost per additional patient retained in care was estimated at US $53 [80].In Tanzania, a package of linkage services that included peer-delivered case management and treatment navigation was estimated to cost US $49 per-client in communities and facility settings overall, and US $20 for a facility-only model where tasks were shifted from nurses to expert-client counsellors [74].In Kenya, the ICER for partner services was $1255 and $956 per DALY averted under programme and task-shifting scenarios, respectively [83].In the Democratic Republic of Congo, the ICER associated with $5 incentives for linking to prevention of mother to child transmission (PMTCT) was $669 and $1156 per additional woman taking PMTCT services and retained in PMTCT care, respectively, compared to standard of care [82].
In Peru, the ICER associated with rapidly linking treatmenteligible PLHIV to CD4 cell count testing and ART compared to standard of care was $1580 per quality adjusted life year [84].

Qualitative values and preferences
Seven linkage to care studies reported qualitative results (12%, n = 7/57) (Table 6).In two studies on cash-based incentives (∼$25) in the United States and South Africa, participants felt that while incentives may increase linkage to care, they may also elicit ethical discussions [86,87].Two studies from South Africa reported qualitative results from multiple interventions.One evaluating integrated POC CD4 cell count testing, transport support and care facilitation reported improved psychosocial support from care facilitation that promoted engagement in care [85].However, though transport cost reimbursement was appreciated by many participants, it was not the only means for managing transport costs for those who could either walk to the clinic or borrow money to pay for transport.The other, evaluating virtual peer mentorship (WhatsApp and SMS) among adolescents and youth, showed that even though mentees valued virtual mentorship, they preferred hybrid models allowing some degree of direct human interaction [73].
Three studies separately reported on qualitative results from peer-based, virtual interventions, and case management.In a Uganda-based study evaluating HIVST distribution through trained community peer-leaders, social network members reported that HIVST increased access to HTS, and the privacy and confidentiality of HIV test results [90].A US-based formative study evaluating the development of a smartphone application to support HIVST use among MSM and transgender women showed potential to address ongoing concerns about the use of HIVST, such as correct reading of results, and linkage to HIV care [89].Lastly, in a Ukrainebased strengths-based case management study, interviewees saw linkage coordinators as accessible health specialists helping clients navigate the complicated healthcare system [88].

D I S C U S S I O N
In this scoping review, we reviewed 66 studies, nine on linkage to HIV prevention and 57 on linkage to care.Despite the availability of a wide range of HIV prevention interventions, there is a dearth of literature on HIV prevention programmes and on the use of HIV messaging about the effectiveness of treatment for prevention [91].Because no single HIV prevention intervention is sufficient to control HIV, prevention packages tailored to population needs are required.Fifty-seven linkage to care studies were identified, mainly from Africa and the Americas.Linkage to care studies focused primarily on streamlined interventions and case management and generally improved linkage to care and ART initiation.No studies were reported from the eastern Mediterranean region where only 41% of PLHIV knew their status, 27% of those aware were on ART and 24% of those on ART were virally suppressed as of 2021 [92].
Studies on streamlined interventions involved same-day HIV testing, ART initiation, and POC CD4 and/or viral load testing and focused mainly on heterosexual African adults receiving community-based testing, and on pregnant women and mothers receiving ART within integrated ANC settings.Streamlined interventions support WHO's recommendations on same-day ART initiation among PLHIV, reducing the time to viral suppression [93].However, some people may not want to initiate ART on the same day as their HIV diagnosis.Therefore, effective linkage to ART support services should be provided for PLHIV who re-test positive in HTS [93].Successful streamlined linkage to ART interventions could be leveraged to support same-day PrEP initiation among higher-risk individuals testing HIV negative.And because there was no difference in linkage to ART when comparing home-based to mobile-clinic-based HTS, or before, during and after clinical consultation, there is an opportunity to diversify HTS settings to suit client preferences [42,43].
Studies on HIV case management involved linkage coordinators developing personalized HIV care and risk reduction plans for clients mainly reported among key populations in the United States and Europe.Overall, HIV case management improved linkage to care and ART initiation highlighting the need for people-centred care in HIV programmes [3].However, while HTS for hospitalized patients is standard practice, intense inpatient case management may not be as effective in improving linkage to care compared to post-discharge followup, highlighting the importance of ongoing client support in the community [50].People-centred strategies were also favoured by clients receiving partner services, peer-based, and multiple interventions that fast-tracked HTS and ART initiation and provided ongoing counselling [13].Such approaches provide ongoing support to higher-risk HIV-negative individuals seeking combination HIV prevention strategies based on their needs and perceived risk.
Studies evaluating virtual interventions showed mixed results.In a Thai study among MSMs, participants receiving online HIVST support were less likely to link to care compared to those receiving either a hybrid (offline HTS and online counselling) or in-person HIV testing and counselling [78].A US-based study among prisoners using case management with video conferencing showed no impact on linkage to care [72].In qualitative studies, participants found virtual interventions acceptable but preferred hybrid formats that incorporated direct human interaction [73].Policymakers, therefore, may need to provide some elements of direct human interaction or innovative ways to continue follow-up when designing virtual strategies for HIV negative.
While previous studies have confirmed that financial incentives may increase HIV testing uptake in the short-term, in general, cash-based incentives did not seem to consistently improve linkage to care or ART initiation [56,57,94].While they were appreciated by participants, they elicited ethical discussions on who can be influenced by money and what can be bought if other alternatives to access healthcare were available, for example borrowing money for transport or walking to healthcare facilities [87].WHO does not recommend financial incentives for clients in general because of cost, sustainability and ethical considerations.
QI studies, involving staff training to improve HTS delivery and data quality, did not seem to improve linkage to care or ART initiation [62,63].In these cluster-RCT studies, there was a high risk of contamination if the staff shared QI strategies across different clusters.As no QI studies were reported on linkage to prevention, other research designs, for example pre-post intervention studies, might be more helpful in reviewing the effectiveness of QI strategies.
Our scoping review has several limitations.First, we limited our search to articles written in English, potentially excluding articles in other languages and introducing bias in the geographical distribution of published research.Second, there was significant variation in the definitions of linkage to prevention and care and in delivery approaches applied across studies.Third, although our search strategy was extensive, this was not a systematic review; therefore, relevant articles could have been missed, and the methodological quality of the included studies such as the risk of bias was not assessed.Fourth, we excluded articles that focused solely on viral load suppression.However, the studies we reviewed on ART initiation may indicate interventions that support eventual viral suppression.Finally, there was a paucity of studies on linkage to screening for non-HIV conditions, with only one reference on linkage to cervical cancer screening, indicating a gap for further research.

C O N C L U S I O N S
This scoping review provides an overview of linkage to prevention and care interventions.Despite a wide range of successful approaches to support linkage to care and ART, few studies provide global guidance on increasing linkage to prevention.As high-burden countries reach the UNAIDS 95-95-95 targets, HIV incidence is declining but not sufficient to substantially reduce new acquisitions by 2030 [2].Differentiated approaches for linkage to prevention, care and treatment are essential based on the epidemiological context, population group and individual risk.Although effective linkage to care interventions may offer insights on how to design combination HIV prevention packages, greater effort to generate evidence to optimize linkage to prevention is a global priority.

A C K N O W L E D G E M E N T S
We are grateful to Anjuli Wagner, University of Washington, and Hunied Kautsar, John Hopkins University, who gave extensive feedback on the design and approach to this scoping review.

F U N D I N G
This work was funded by the Bill and Melinda Gates Foundation INV-024432.

D I S C L A I M E R
The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.The views expressed in this article are those of the authors and do not represent the views of the WHO.

D ATA AVA I L A B I L I T Y S TAT E M E N T
Data sharing is not applicable to this article because it is a review, and no new data were generated during the current study.The protocol is available on request from the corresponding author.

PAT I E N T A N D P U B L I C I N VO LV E M E N T
Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans for this research.

P R OV E N A N C E A N D P E E R R E V I E W
Not commissioned, externally peer-reviewed.

Figure 2 .
Figure 2. Map of studies included in scoping review, by country.In Africa, Lesotho (n = 2) and Eswatini (n = 1) are too small to appear on the map.The nine linkage to prevention studies were conducted in the United States [4] and in Africa (Kenya [n = 2], Zambia, Malawi and Zimbabwe).

Figure 5 .
Figure 5. HIV testing strategy by intervention and delivery approach.

Table 3 . (Continued) Study Population, type of testing Delivery approach Description Results
Intervention: Participants were introduced to the Linkage Coordinator (LC)-a trained nurse who provided the MARTAS (Modified ARTAS) where ARTAS was an individual-level, multi-session case management linkage-to-care intervention, based on the Strengths-based Case Management (SBCM) model Standard of care: Verbal referrals to a network Peer case managers where delivered the intervention via five one-on-one sessions over a 6-month period.Standard of care: Resource card containing harm reduction information and contact information

Table 3 . (Continued) Study Population, type of testing Delivery approach Description Results
Linkage to care: 57% of participants in the CIS group achieved the primary outcome versus 35% of those in the standard of care, SOC group (RR CIS vs. SOC = 1.58, 95% CI 1.05-2.39).
Intervention: Project Bridge (PB): Case managers and social workers were assigned to provide intensive case management and weekly sessions to participants for 3 months with follow up at 6 and 12 months post randomization.Standard of care: Standard referral to treatment.(HCT), that is personalized risk assessment and risk reduction plan.In both intervention and control groups, HIV-positive individuals were given referrals to HIV/AIDS clinics for follow-up care Standard of care: Outpatient HCT 1-(CIS) included (1) real-time, point-of-care CD4 test results; (2) patients with CD4 cell count < = 350 cells/mm 3 were provided with accelerated ART initiation; (3) health messages and appointment reminders via SMS; and (4) patients in the CIS-positive cohort received the CIS plus non-cash financial incentives (Fis), that is prepaid cellular air-time cards Standard of care: Managed as per prevailing Ministry of Health guidelines + testing at the time of an HIV-positive test, accelerated antiretroviral therapy (ART) initiation for treatment-eligible participants, mobile phone appointment reminders, health educational packages and non-cash financial incentives.Standard of care: Post-test counselling and referral to an HIV clinic using a national referral form

Table 3 . (Continued) Study Population, type of testing Delivery approach Description Results
Intervention: Point-of-care group with same-day point-of-care CD4 cell count testing at enrolmentEligible HIV-positive participants (aged ≥16 years) were randomly assigned (1:1:1) to receive 1. Lay counsellor follow-up arm: Participants received visits at home at months 1, 3 and 6. 2. Clinic facilitation arm: A lay counsellor met HIV-positive people at the clinic and explained the steps of engagement in care and benefits of ART or 3. Standard of care (Referral arm): Referral to local HIV clinics to obtain their count.

Table 3 . (Continued) Study Population, type of testing Delivery approach Description Results
Abbreviation: HIVST, HIV self-testing; MSM, men who have sex with men; PMTCT, prevention of mother to child transmission; PWID, persons who inject drugs; RCT, Randomized controlled trial; TB, tuberculosis

Table 4 . (Continued) Study Population, type of testing Delivery approach Description Result type Effect type Effect size
Abbreviation: HIVST, HIV self-testing; MSM, men who have sex with men; PWID, persons who inject drugs; PMTCT, prevention of mother to child transmission; RCT, Randomized controlled trial